A UISegmentedControl object is a horizontal control made of multiple segments, each segment functioning as a discrete button. A segmented control affords a compact means to group together a number of controls.

A segmented control can display a title (an NSString object) or an image (UIImage object). The UISegmentedControl object automatically resizes segments to fit proportionally within their superview unless they have a specific width set. When you add and remove segments, you can request that the action be animated with sliding and fading effects.

How you configure a segmented control can affect its display behavior:

If you set a segmented control to have a momentary style, a segment doesn’t show itself as selected (blue background) when the user touches it. The disclosure button is always momentary and doesn’t affect the actual selection.

In versions of iOS prior to 3.0, if a segmented control has only two segments, then it behaves like a switch—tapping the currently-selected segment causes the other segment to be selected. On iOS 3.0 and later, tapping the currently-selected segment does not cause the other segment to be selected.

Customizing Appearance

In iOS v5.0 and later, you can customize the appearance of segmented controls using the methods listed in Customizing Appearance. You can customize the appearance of all segmented controls using the appearance proxy (for example, [UISegmentedControl appearance]), or just of a single control.

When customizing appearance, in general, you should specify a value for the normal state of a property to be used by other states which don’t have a custom value set. Similarly, when a property is dependent on the bar metrics (on the iPhone in landscape orientation, bars have a different height from standard), you should make sure you specify a value for UIBarMetricsDefault.

In the case of the segmented control, appearance properties for UIBarMetricsLandscapePhone are only respected for segmented controls in the smaller navigation and toolbars that are used in landscape orientation on the iPhone.

Declaration

Discussion

The default value is UISegmentedControlNoSegment (no segment selected) until the user touches a segment. Set this property to -1 to turn off the current selection. UISegmentedControl ignores this property when the control is in momentary mode. When the user touches a segment to change the selection, the control event UIControlEventValueChanged is generated; if the segmented control is set up to respond to this control event, it sends a action message to its target.

Discussion

If backgroundImage is not an image returned from resizableImageWithCapInsets:, the cap width is calculated by subtracting one from the image's width then dividing by 2. The cap widths are used as the margins for text placement. To adjust the margin, use the margin adjustment methods.

Declaration

Parameters

attributes

The text attributes of the title for state.

state

A control state.

Discussion

The attributes dictionary can specify the font, text color, text shadow color, and text shadow offset for the title in the text attributes dictionary, using the keys in NSString UIKit Additions Reference.